Dont start host user creation if any required binaries are not found

lib/srv/sess.go

@@ -263,7 +263,7 @@ func (s *SessionRegistry) TryWriteSudoersFile(ctx *ServerContext) error {
 }
 
 func (s *SessionRegistry) TryCreateHostUser(ctx *ServerContext) error {
-	if !ctx.srv.GetCreateHostUser() {
+	if !ctx.srv.GetCreateHostUser() || s.users == nil {
 		s.log.Debug("Not creating host user: node has disabled host user creation.")
 		return nil // not an error to not be able to create host users
 	}

lib/srv/usermgmt.go

@@ -43,7 +43,7 @@ func NewHostUsers(ctx context.Context, storage *local.PresenceService, uuid stri
 	//nolint:staticcheck // SA4023. False positive on macOS.
 	backend, err := newHostUsersBackend()
 	switch {
-	case trace.IsNotImplemented(err):
+	case trace.IsNotImplemented(err), trace.IsNotFound(err):
 		log.Debugf("Skipping host user management: %v", err)
 		return nil
 	case err != nil: //nolint:staticcheck // linter fails on non-linux system as only linux implementation returns useful values.
@@ -473,14 +473,15 @@ func (u *HostUserManagement) UserCleanup() {
 	cleanupTicker := time.NewTicker(time.Minute * 5)
 	defer cleanupTicker.Stop()
 	for {
-		if err := u.DeleteAllUsers(); err != nil {
-			if trace.IsNotFound(err) {
-				log.Debugf("Error during temporary user cleanup: %s, stopping cleanup job", err)
-				return
-			} else {
-				log.Error("Error during temporary user cleanup: ", err)
-			}
+		err := u.DeleteAllUsers()
+		switch {
+		case trace.IsNotFound(err):
+			log.Debugf("Error during temporary user cleanup: %s, stopping cleanup job", err)
+			return
+		case err != nil:
+			log.Error("Error during temporary user cleanup: ", err)
 		}
+
 		select {
 		case <-cleanupTicker.C:
 		case <-u.ctx.Done():

lib/srv/usermgmt_linux.go

@@ -22,6 +22,7 @@ import (
 	"bufio"
 	"fmt"
 	"os"
+	"os/exec"
 	"os/user"
 	"path/filepath"
 	"strconv"
@@ -48,6 +49,16 @@ type HostSudoersProvisioningBackend struct {
 
 // newHostUsersBackend initializes a new OS specific HostUsersBackend
 func newHostUsersBackend() (HostUsersBackend, error) {
+	var missing []string
+	for _, requiredBin := range []string{"usermod", "useradd", "getent", "groupadd", "visudo"} {
+		if _, err := exec.LookPath(requiredBin); err != nil {
+			missing = append(missing, requiredBin)
+		}
+	}
+	if len(missing) != 0 {
+		return nil, trace.NotFound("missing required binaries: %s", strings.Join(missing, ","))
+	}
+
 	return &HostUsersProvisioningBackend{}, nil
 }